The consumer products ratings publication gave the $104,000 sedan a "worse-than-average" rating in its new, annual report about the predicted reliability of new vehicles.
The announcement, initially made in Detroit at an Automotive Press Association meeting, contrasted sharply with Consumer Reports' initial rating of Tesla's all-electric sedan.
In August, the publication gushed about the Model S P85D, saying it was "the best car" it ever tested. It gave the sedan a 103 score out of 100 points.
"The car set a new benchmark, so we had to make changes to our scoring to account for it," Consumer Reports said.
The publication, however, updated its review of the car after it received the results of a survey from 1,400 Model S owners, who chronicled "an array of detailed and complicated maladies."
Owner complaints included rattles, leaks, and problems with the charging equipment, drivetrain and center console displays. The main problem areas involved the drivetrain, power equipment, charging equipment, giant iPad-like center console, and body and sunroof squeaks, rattles, and leaks.
The Tesla Model S wasn't the only high-performance vehicle that sank to a below-average reliability rating. Others include the BMW X5 and 5 Series, and the Chevrolet Corvette.
"When automakers roll out new technology, be it infotainment, transmissions, or engine variations, it often has a deleterious effect on vehicle reliability. Tesla is not only the poster child for a new type of high-performance, high-mileage EV, but it also has been adding complex new variations as assembly-line updates, such as all-wheel drive this year," Consumer Reports said. "So it's not surprising to see problems continue to crop up."
Regardless of complaints, Consumer Reports' customer ratings page still placed the Tesla Model S P85D at the very top of the list, with a 97% satisfaction score.
The next closest car to the Model S in the customer satisfaction ratings was the Audi A7 with an 84% rating.
Nevertheless, survey respondents focused on specific areas that scored worse on this year's model compared to that of the 2014 model in the previous year's survey. Respondents said most problems were related to climate control, steering and suspension systems.
Other problems owners noted were inoperable wipers, leaking battery cooling pumps, out-of-alignment trunk and hatchback latches, and persistent wheel-alignment issues.
Complaints about the drive system have also increased as the Model S cars have aged -- specifically for the 2013 model, which was the car's first full model year, the magazine said.